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EXPERIMENTS WITH DIRIGIBLE

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Originally appearing in Volume V01, Page 270 of the 1911 Encyclopedia Britannica.
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EXPERIMENTS WITH DIRIGIBLE BALLOONS See also:

Giffard, the future inventor of the See also:injector, devised a See also:steam-See also:engine weighing, with See also:fuel and See also:water for one See also:hour, 154 lb per See also:horse-See also:power, and was bold enough to employ it in proximity to a See also:balloon inflated with See also:coal See also:gas. He was not able to See also:stem a See also:medium See also:wind, but attained some deviation. He repeated the experiment in 1855 with a more elongated spindle, which proved unstable and dangerous. During the See also:siege of See also:Paris the See also:French See also:government decided to build a navigable balloon, and entrusted the See also:work to the See also:chief See also:naval constructor, See also:Dupuy de Lome. He went into the subject very carefully, made estimates of all the strains, resistances and speeds, and tested the balloon in 1872. Deviations of 12° were obtained from the course of a wind blowing 27 to 37 M. per hour. The See also:screw propeller was driven by eight labourers, a steam-engine being deemed too dangerous; but it was estimated that had one been used, weighing as much as the men, the See also:speed would have been doubled. Tissandier and his See also:brother applied an electric motor, lighter than any previously built, to a spindle-shaped balloon, and wenf up twice in 1883 and 1884. On the latter occasion he stemmed a wind of 7 M. per hour. The See also:brothers abandoned these experiments, which had been carried on at their own expense, when the French See also:War See also:Department took up the problem. See also:Renard and Krebs, the See also:officers in See also:charge of the War Aeronautical Department at See also:Meudon, built and experimented with in 1884 and 1885 the fusi-See also:form balloon " La See also:France," in which the " See also:master " or maximum See also:section was about one-See also:quarter of the distance from the stem. The propelling screw was at the front of the See also:car and driven by an electric motor of unprecedented lightness.

Seven ascents were made on very See also:

calm days, a maximum speed of 14 M. an hour was obtained, and the balloon returned to its starting-point on five of the seven occasions. Subsequently another balloon was constructed, said to be capable of a speed of 22 to 28 m. per hour, with a different motor. After many years of experiment Dr Wolfert built and experimented with in See also:Berlin, in 1897, a See also:cigar-shaped balloon driven by a gasoline motor. An See also:explosion took See also:place in the See also:air, the balloon See also:fell and Dr Wolfert and his assistant were killed. It was also in 1897 that an See also:aluminium balloon was built from the designs of D. See also:Schwarz and tested in Berlin. It was driven by a Daimler benzine motor, and attained a greater speed than " La France "; but a See also:driving See also:belt slipped, and in coming down the balloon was injured beyond repair. From 2897 onwards See also:Count See also:Ferdinand von Zeppelin, of the See also:German See also:army, was engaged in constructing an immense balloon, truly an airship, of most careful and most intelligent See also:design, to carry five men. It consisted of an aluminium framework containing sixteen gas bags with a See also:total capacity of nearly 400,000 cub. ft., and it had two cars, each containing a 16 h.p. motor. It was first tested in See also:June 1900, when it attained a speed of 18 m. an hour and travelled a distance of 31 M. before an See also:accident to the steering See also:gear necessitated the discontinuance of the experiment. In 1905 Zeppelin built a second airship which had a slightly smaller capacity but much greater power, its two See also:motors each developing 85 h.p. This, after making some successful trips, was wrecked in a violent See also:gale, and was succeeded by a third airship, which, at its trial in See also:October 2906, travelled See also:round See also:Lake See also:Constance and showed itself able to execute numerous curves and traverses.

At a second See also:

series of trials in See also:September 1907, after some alterations had been effected, it attained a speed of 36 m. an hour, remaining in the air for many See also:hours and carrying nine or eleven passengers. A See also:fourth See also:vessel of similar design, but with more powerful motors, was tried in 2908, and succeeded in travelling 250 M. in 11 hours, but owing to a See also:storm it was wrecked when on See also:land and burnt at Echterdingen on the 5th of See also:August. Subscriptions, headed by the See also:emperor, were at once raised to enable Zeppelin to build another. Meanwhile in 1901 Alberto See also:Santos See also:Dumont had begun experiments with dirigible balloons in Paris, and on the 19th of October won the See also:Deutsch See also:prize by steering a balloon from St See also:Cloud round the Eiffel See also:tower and back in See also:half an hour, encountering on his return See also:journey a wind of nearly 5 metres a second. An airship constructed by See also:Pierre and See also:Paul Lebaudy in 1904 also made a number of successful trials in the vicinity of Paris; with a motor of 40 h.p., its speed was about 25 M. an hour, and it regularly carried three passengers. In October 1907 the " Nulli See also:Secundus," an airship constructed for the See also:British War See also:Office, sailed from See also:Farnborough round St Paul's See also:Cathedral, See also:London, to the Crystal See also:Palace, See also:Sydenham, a distance of about 50 m., in 3 hours 35 minutes. The See also:weight carried, including two occupants, was 3400 lb, and the maximum speed was 24 M. an hour, with a following wind of 8 m. an hour. Thus the principles which govern the design of the dirigible balloon may be said to have been evolved. As the lifting power grows as the See also:cube of the dimensions, and the resistance approximately as the square, the See also:advantage lies with the larger sizes of balloons, as of ocean steamers, up to the limits within which they may be found practicable. Count Zeppelin gained an ad-vantage by attaching his propellers to the balloon, instead of to the car as heretofore; but this requires a rigid framework and a See also:great increase of weight. Le Compagnon endeavoured, in 1892, Dirigible balloons. Dia- See also:Con- Lifting Weight Weight Speed See also:Year.

Inventor. Length. See also:

meter. Capa- of of H.P. per tents. See also:city. Balloon. Motor. hour. Ft. Ft. Cub. ft. lb. lb. lb. See also:Miles. 1852 Giffard d . . 144 39 88,300 3,978 2,794 462 3.0 6.71 7 Dupuy de Lome .

. . 118 49 120,088 8,358 4,728 2000 o•8 6.26 1884 Tissandier 92 30 37,439 2,728' 933 616 1.5 7.82 1885 Renard and Krebs . . 165 27 65,836 4,402 2,449 174 9.0 14.00 1897 Schwarz . . 157 ) 346 9 130,500 8,133 6,800 Soo? 16•o 17.00 1900 Zeppelin I. 420 39 400,000 25,000 19,000 1500 32.0 18.00 1901 Santos Du- mont VI. 108 20 22,200 .. .. .. 16.20 19.00 1908 " Republique " 195 35 130,000 3,100 .. .. 8o 3o 1908 Zeppelin IV.

. 446 421 450,000 .. .. .. 220 270 to substitute flapping wings for rotary propellers, as the former can be suspended near the centre of resistance. C. Danilewsky followed him in 1898 and 1899, but without remarkable results. Dupuy de Lome was the first to estimate in detail the resistances to balloon propulsion, but experiment showed that in the aggregate they were greater than he calculated. Renard and Krebs also found that their computed resistances were largely exceeded, and after revising the results they gave the See also:

formula R=o•o1685 D2V2, R being the resistance in kilograms, D the See also:diameter in metres and V the velocity in metres per second. Reduced to British See also:measures, in pounds, feet and miles per hour, R= o•0006876 D2V2, which is somewhat in excess of the formula computed by Dr See also:William See also:Pole from Dupuy de Lome's experiments. The above coefficient applies only to the shape and See also:rigging of the balloon " La France,” and combines all resistances into one See also:equivalent, which is equal to that of a See also:flat See also:plane 18/0 of the " master section.” This coefficient may perhaps hereafter be reduced by one-half through a better form of See also:hull and car, more like a See also:fish than a spindle, by diminished sections of suspension lines and See also:net, and by placing the propeller at the centre of resistance. To compute the results to be expected from new projects, it will be preferable to estimate the resistances in detail. The following table shows how this was done by Dupuy de Lome, and the probable corrections which should have been made by him: RESISTANCES—DUPUY DE LOME'S BALLOON Computed by Dupuy de Lome.

MoreProbableValues. V = 2.22 in. per sec. V = 2.82 m. per sec. See also:

Part. See also:Area, Co- Air Resist- Co- Air Resist- Sq. effici- Pres- ance, effici- Pres- ance, Metres. ent. sure. Kg. ent. sure. Kg. Hull, with- 172.96 ,/3o 0.665 3.830 1/15 0.875 IO.091 out net. . Car 3.25 1/5 ,, 0.432 1/5 ,, 0.569 Men's bodies 3.00 1/5 „ 0.400 1/2 „ 1.312 Gas tubes . 6.4o 1/5 „ 0.850 1/2 „ 2.750 Small cords Io•oo 1/2 3.325 1/2 ,, 4.375 Large cords 9.90 1/3 2.194 1/3 „ 2.887 11.031 .2P984 When the resistances have been reduced to the lowest possible minimum by careful design, the attainable speed must depend upon the efficiency of the propeller and the relative lightness of the motor. The commercial uses of dirigible balloons, however, will be small, as they must remain housed when the wind aloft is brisk. The sizes will be great and costly, the loads small, and the See also:craft frail and See also:short-lived, yet dirigible balloons constitute the obvious type for governments to evolve, until they are superseded by efficient flying See also:machines.

(See further, as to the latter, the See also:

article See also:FLIGHT AND FLYING.) The chief danger attending ballooning lies in the descent; for if a strong wind be blowing, the grapnel will sometimes trail for miles over the ground at the See also:rate of ten or twenty miles Practice an hour, catching now and then in hedges, ditches, roots t aero- s tation. tion. of trees, &c.; ; and, after giving the balloon a terrible s jerk, breaking loose again, till at length some obstruction, such as the wooded See also:bank of a stream, affords a See also:firm hold. This danger, however, has been much reduced by the use of the " ripping-See also:cord,” which enables a See also:panel to be ripped open and the balloon to be completely deflated in a few seconds, just as it is reaching the See also:earth. But even a very rough descent is usually not productive of any very serious consequences; as, although the occupants of the car generally receive many bruises and are perhaps cut by the See also:ropes, it rarely happens' that anything worse occurs. On a See also:day when the wind is See also:light (supposing that there is no want of See also:ballast) nothing can be easier than the descent, and the aeronaut can decide several miles off on the See also:field in which he will alight. It is very important to have a See also:good See also:supply of ballast, so as to be able to check the rapidity of the descent, as in passing downwards through a wet cloud the weight of the balloon is enormously increased by the water deposited on it; and if there is no ballast to throw out in See also:compensation, thevelocity is sometimes very great. It is also convenient, if the See also:district upon which the balloon is descending appear unsuitable for landing, to be able to rise again. The ballast consists of See also:fine baked See also:sand, which becomes so scattered as to be inappreciable before it has fallen far below the balloon. It is taken up in bags containing about i cwt. each. The balloon at starting is liberated by a See also:spring catch which the aeronaut releases, and the ballast should be so adjusted that there is nearly See also:equilibrium before leaving, else the rapidity of ascent is too great, and has to be checked by parting with gas. It is almost impossible to liberate the balloon in such a way as to avoid giving it a rotary See also:motion about a See also:vertical See also:axis, which continues during the whole See also:time it is in the air. This rotation makes it difficult for those in the car to discover in what direction they are moving; and it is only by looking down along the rope to which the grapnel is suspended that the motion of the balloon over the See also:country below can be traced. The upward and downward motion at any instant is at once known by merely dropping over the See also:side of the car a small piece of See also:paper: if the paper ascends or remains on the same level or stationary, the balloon is descending; while, if it descends, the balloon is ascending.

This test is exceedingly delicate.

End of Article: EXPERIMENTS WITH DIRIGIBLE

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